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Electromagnetic
Energy |
Induction (EMI) |
| Radio Frequency (RFI) |
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800.440.6374 Phone 360.835.7507
sales@wovenwire.com |
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Electromagnetic
Iinterference |
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Electromagnetic interference is a disturbance that affects an
electrical circuit due to either electromagnetic induction or electromagnetic
radiation emitted from an external source.
The disturbance may obstruct, degrade or
reduce the
effective performance of the circuit. The source may artificial
or natural, capable of producing rapidly changing electrical currents, such as an
electrical circuit, the Sun
or the
Northern Lights. |
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| EMI can be intentionally used for radio jamming, as in
some forms of
electronic warfare, or may occur unintentionally,
resulting from spurious emissions
such as
intermodulation distortion (IMD)
devices. It
typically affects the reception of
AM radio, Cell Phones, FM radio and
Television reception. |
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| EMI or RFI
are generally categorized as
either "Narrowband" or
"Broadband" |
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| Narrowband interference usually arises from intentional
transmissions such as radio, TV,
Cell Phone and Pager transmitters. |
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| Broadband interference
typically results from incidental radio
frequency emitters such as
electrical transmission lines, electric motors,
welders, thermostats and even insect
zappers. Applications
where electrical power is cycled on and off
rapidly is a potential source. The spectra of these sources generally
resemble that of synchrotron sources, stronger at low frequencies and
diminishing at higher frequencies, though this noise is often modulated,
or varied, by the creating device in some way. Included in this category
are computers and other digital equipment as well as televisions. The rich
harmonic content of these devices means that they can interfere over a
very broad spectrum. Characteristic of broadband RFI is an inability to filter it
effectively once it has entered the
receiver chain. |
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| Conducted electromagnetic interference is caused by the physical
contact of the conductors as opposed to radiated EMI which is caused by
induction (without physical contact of the conductors). Electromagnetic
disturbances in the EM field of a conductor will no longer be confined to
the surface of the conductor and will radiate away from it. This persists
in all conductors and mutual inductance between two radiated
electromagnetic fields will result in EMI. |